Secret of the Ghost Rig

Plot

Crystal Cove is terrorized by a mysterious Ghost Truck that has been running people off the highways. Meanwhile, Fred is helping his dad who is running for reelection against George Avocados. Daphne's parents are trying to set Daphne up with Rung Ladderton, the heir to a ladder company. During all this, many crystal doorknobs have been stolen. Later, while the gang is driving the Mystery Machine, the Ghost Truck rams them off the road. Surviving with no damage, they contact the police. Fred then uses Daphne's phone to take pictures of tire tracks. He sends them to Angel Dynamite, who confirms the only people in town who own those tires are G. Nurno Treddel and George Avocados. While the others follow George, Daphne is on her date with Rung at the Bloody Steak. Late, he arrives moments before the others arrive from an encounter with the truck. After Rung leaves, Scooby finds a CD from Mr. E in a menu. Listening to it, he mentions a diamond, which relates to how George Avocados's father stole a diamond and disguised it as a crystal doorknob. Leaving, they soon discover a set of tire tracks ending at a mountainside. Unlocking a secret cavern, they find all the missing crystal doorknobs plus a journal that belonged to George Avocados's father with a confession to the theft of the diamond. The truck then appears and chases the gang to City Hall. Fred's traps he set up earlier capture the truck in a large pool with a shark. The driver is then revealed to be Rung Ladderton, who wanted the diamond to make money since his ladder company will soon be going bankrupt. Velma points out that the other person Angel mentioned to have bought the tires, G. Nurno Treddal was Rung Ladderton spelled backwards. The next day, Mayor Fred Jones Sr. announces that Mystery Inc. ruined yet another tourist attraction but saved the stolen diamond. Mayor Jones then appoints Scooby as a chief of pizza affairs.